1. Field of the Invention
The present invention relates to access control method and device of a light spot in an optical disk drive unit. More particularly, the present invention relates to access control method and device of a disk drive unit in which a light spot can be accessed at a high speed and can be accurately positioned onto a target track.
2. Description of the Related Art
In a general well-known access method, a light spot is formed on a disk and a track-crossing signal is detected when light of the spot reflected on the disk crosses a track of the disk A moving speed of the light spot is controlled by using this track-crossing signal such that the light spot is accessed in a radial direction of the disk in accelerating and decelerating modes.
For example, Japanese Patent Application Laying Open (KOKAI) No. 2-33731 shows an optical disk drive unit having a seek motor for moving an optical head and a tracking driving means for slightly displacing a light spot. In this optical disk drive unit, a moving speed of the light spot is controlled by the tracking driving means using a tracking pulse obtained from light of the spot reflected on the disk when the light spot crosses a track of the disk. An operation of the seek motor is controlled such that the operation of the seek motor follows a movement of the tracking driving means, thereby performing an accessing operation of the light spot.
In this optical disk drive unit, a reference speed compared with the moving speed of the light spot is slowly increased from beginning of the accessing operation and is slowly decreased in the course of the accessing operation. Accordingly, no movement of the tracking driving means is excessively accelerated so that the operation of the seek motor easily follows the movement of the tracking driving means.
The reference speed must be changed at an acceleration considerably smaller than an allowable maximum acceleration of the seek motor to make the operation of the seek motor follow the movement of the tracking driving means.
This is because no operation of the seek motor can follow the movement of the tracking driving means when there are disturbances such as vibrations and eccentricity of tracks, etc.
As a result, the light spot can be accelerated only at an acceleration considerably smaller than a maximum limit of accelerating ability of the light spot, thereby increasing access time.
Accordingly, the general access control method and device have disadvantages that no light spot can be accessed at a high speed.